1. Field of the Invention
The present invention provides a method for producing an iron oxide weighting material from an iron chloride solution. The weighting material is useful, among other things, in a drilling fluid.
2. Brief Description of the Prior Art
In drilling operations by the rotary method, a drilling fluid is maintained in the hole at all times. During actual drilling the fluid continuously is circulated downwardly through the hollow stem of the drill rod and emerge at the bottom of the hole through passages in the drill bit mounted on the end of the drill rod. The drilling fluid then rises to the surface through the annular space between the drill rod and the wall of the hole and flows into a surface pit for recirculation.
The drilling fluid is required to: (i) lift cuttings from the hole; (ii) control well pressures; and (iii) cool the bit. The removal of rock chips from the cutting face of the bit and the transport of these cuttings to the surface are dependent upon the flow properties of the drilling fluid and the velocity of its movement. Control of entry of fluids such as gas, oil and water into the well from the underground formation is dependent upon the hydrostatic pressure exerted by the drilling fluid.
To prevent the uncontrolled flow of fluids from the underground formation into the well, the drilling fluid must have sufficient density to provide a pressure greater than that exerted by the formation fluids. The greater the density of the drilling fluid, the greater the buoyant effect on the rock cuttings and thus the greater the carrying capacity of the fluid, that is, the quantity of rock cuttings that can be suspended in a given volume of the drilling fluid. The carrying capacity of the drilling fluid depends upon the relationship between shear stress and shear rate that exists under the conditions of flow. The density of the drilling fluid must not be carried too high because excessive hydrostatic pressure can cause the loss of circulation through the well.
Normally, the formation fluids are under pressure at least equal to that of a column of water of equal depth so that densities in excess of water alone are required. To obtain greater densities, materials referred to as "weighting materials" are added to drilling fluids. The most extensively used material for increasing the density of a drilling fluid is ground barite, the common mineral form of barium sulfate. It also is known that iron oxides can be used to replace a portion or all of the barite used as a weighting material in a drilling fluid.
U.S. Pat. No. 2,003,701 discloses the use of from 2 to 10 percent by weight of iron oxide in a bentonite-containing drilling fluid. Patentee states that the addition of rough cellular flake or sponge-like iron oxide to the drilling fluid produces a material increase in the strength of the fluid when used as a hole wall lining in comparison to bentonite alone.
U.S. Pat. No. 3,041,276 discloses a drilling fluid composition comprising a clay-free aqueous suspension containing from about 3 to 8 parts of smelter by-product per part of water. The smelter by-product comprises iron and arsenic in a ratio from about 1.5:1. Patentee states that the smelter by-product and water form a firm gel structure having a weight in the range of from 19 to 32 pounds per gallon.
U.S. Pat. No. 3,887,474 discloses a process for producing iron oxide suitable for use as a weighting agent in drilling fluids from an iron and sulfur containing mineral mass. The mineral mass is roasted to produce iron oxide solids containing less than 2 percent by weight sulfur. The roasted solids are quenched from a temperature above 200.degree. C. to a level below 100.degree. C. while excluding any oxidizing atmosphere. The quenched solids are washed and leached to remove water soluble components and then milled. The milled solids are classified to a particle size below 75 microns and a particle size distribution such that no more than 50 percent is below a particle size of 10 microns.
U.S. Pat. No. 4,092,407 discloses a process for producing an iron oxide of limited magnetic susceptibility for use as a weighting agent. An iron oxide material consisting of calcined fine pyrites having a high magnetic susceptibility is fired at a temperature between 1210.degree. C. and 1400.degree. C. in the presence of an oxidizing atmosphere. The firing is of a duration sufficient to reduce the magnetic susceptibility of the solids to a gram magnetic susceptibility below 1000.times.10.sup.- 6. The solids then are slowly cooled to a temperature of at least below 780.degree. C. in an oxidizing atmosphere at a rate of 1.degree. to 30.degree. C. per minute.
U.S. Pat. No. 4,008,775 discloses a process for scavenging hydrogen sulfide during drilling operations by using a drilling fluid containing iron oxide having the composition Fe.sub.3 O.sub.4. Patentee states that the Fe.sub.3 O.sub.4 is prepared by grinding iron ore to a powder and then oxidizing it at a temperature of 400.degree. to 450.degree. F. to form the Fe.sub.3 O.sub.4. The Fe.sub.3 O.sub.4 has a surface area at least 10 times as great as magnetite particles of equal size. The Fe.sub.3 O.sub.4 is admixed with the drilling mud and circulated through the well. The Fe.sub.3 O.sub.4 reacts with the hydrogen sulfide to form a stable pyrite FeS.sub.2. The stable pyrite solids are removed from the drilling mud together with the rock cuttings and the mud then is recirculated.
Various processes, such as steel pickling and titaniferous ore leaching, produce substantial quantities of iron chlorides as by-products through the reaction of iron with hydrochloric acid. It is highly desirable in these processes to recover the hydrochloric acid for recirculation. It would be preferable to recover the hydrochloric acid in a manner such that the iron in the iron chlorides can be converted to a useful material such as iron oxide of a quality suitable for use in drilling fluids.